Many pourable food products, such as fruit juice, pasteurized or UHT (ultra-high-temperature processed) milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material.
A typical example of such a package is the parallelepiped-shaped package for liquid or pourable food products known as TETRA BRIK ASEPTIC (registered trademark), which is formed by folding and sealing laminated strip packaging material. The laminated packaging material comprises layers of fibrous material, e.g. paper, covered on both sides with thermoplastic plastic material, e.g. polyethylene, and, in the case of aseptic packages for long-storage products, such as UHT milk, the side of the packaging material eventually contacting the food product in the package also has a layer of oxygen-barrier material, e.g. a sheet of aluminium or EVOH, which is in turn covered with one or more layers of thermoplastic material.
As is known, such packages are formed on fully automatic packaging machines, on which a continuous tube is formed from the web-fed packaging material; the web of packaging material is sterilized on the packaging machine itself, e.g. by applying a chemical sterilizing agent, such as a hydrogen peroxide solution, which, after sterilization, is removed, e.g. vaporized by heating, from the surfaces of the packaging material; and the web of packaging material so sterilized is maintained in a closed sterile environment, and is folded and sealed longitudinally to form a tube.
The tube is filled with the sterilized or sterile—processed food product, and is sealed and cut at equally spaced cross sections to form pillow packs, which are then folded mechanically to form the finished, e.g. substantially parallelepiped-shaped, packages.
The finished package is provided with an opening device normally defined by a removable opening tab, which is applied to the packaging material before this is fed to the packaging machine where, as stated, it is folded to form a continuous tube and filled with the food product for packaging.
More specifically, the first operation comprises forming an orifice or through hole in the packaging material; the side of the packaging material eventually forming the inside of the package is then fitted with a “patch” over the hole and comprising a small sheet of heat-seal plastic material; and the opposite side of the packaging material is fitted with the removable opening tab, which is heat sealed to the patch. On the side heat sealed to the patch, the tab normally comprises a layer of heat-seal plastic material, e.g. polyethylene. By virtue of the patch and tab adhering to each other, the tab, when pulled off, also removes the part of the patch sealed to it, thus opening the hole.
Alternatively, the through hole may be formed directly in the layer of fibrous material of the packaging material, before the fibrous material layer is laminated with the other packaging material layers hereinafter referred to simply as “lamination layers”.
At the end of the lamination process, the hole is thus covered by the lamination layers, the package is perfectly sound, and a patch is no longer required.
As before, the tab is applied to the side of the packaging material eventually defining the outside of the package, and is sealed to the layer of thermoplastic material covering the hole.
Wedge-shaped sealed packages for pourable food products are also known by the name of TETRA WEDGE (registered trademark), which are also formed from a tube of sheet packaging material sealed and cut along equally spaced cross sections as described above.
Such packages are defined by a flat rectangular base wall; by two isosceles-trapezium-shaped lateral walls projecting from respective opposite sides of the base wall; and by two triangular lateral walls projecting from the other sides of the base wall and forming, with the trapezoidal lateral walls, a wedge-shaped end portion opposite the base wall and including a transverse sealing band of the package.
Wedge-shaped packages of the above type normally have no opening devices, and are widely used in markets in which cost is the main parameter.
On account of the small size of the product outlet hole or the absence of an opening device, such packages are unsuitable for use with highly viscous, semifluid pourable food products, such as yoghurt, cream or soup, or with solidified pourable food products, such as cheese or desserts, which are poured into the package in liquid form and later set inside the package. Such packages, in fact, make it extremely difficult to extract the above products from the outlet holes or from openings torn or cut into the packages, and, above all, do not permit insertion of a spoon by which to scoop out the product.